The present invention relates to completion systems for subsea oil and gas wells, and more specifically, to an apparatus and method for installing conventional completion systems.
The installation of a conventional subsea completion system from a drilling rig typically includes the following steps: (1) install a conductor housing at the sea floor; (2) install a wellhead in the conductor housing; (3) land a blow-out preventer (“BOP”) stack on the wellhead; (4) land various casing hangers and their associated casing strings in the wellhead through the BOP; (5) land a tubing hanger and its associated production tubing string in the wellhead through the BOP using a tubing hanger running tool (“THRT”) suspended from a landing string; (6) install a wireline plug in the production bore of the tubing hanger through the landing string and the THRT; (7) retrieve the THRT; (8) retrieve the BOP; (9) install a christmas tree on the wellhead using an open water riser; (10) retrieve the wireline plug through the open water riser; (11) flow test the well back to the drilling rig through the open water riser; (12) retrieve the open water riser; and (13) install a tree cap on the christmas tree.
In this sequence of steps, the wireline plug is installed in the tubing hanger in step 6 in order to provide an additional barrier between the production bore and the sea when the BOP is removed in step 8. In addition, an open water riser is used to install the christmas tree in step 9 in order to provide a conduit for retrieving the wireline plug in step 10 and for flow testing the well back to the drilling rig in step 11.
Recently operators have increasingly begun flow testing the well back to a normal production facility rather than the drilling rig. This practice eliminates the need to rent well test equipment and transport it to the drilling rig during completion activities. In addition, flow testing the well back to a normal production facility does not require an open water riser. However, such a riser is still required for retrieving the wireline plug from the tubing hanger.
Open water risers are typically run from drilling rigs or similar surface facilities which are relatively expensive to rent and operate. Moreover, since open water risers are usually time consuming to deploy, any well installation step which requires the use of an open water riser will necessarily be costly. Thus, if an alternative existed for retrieving the wireline plug from the tubing hanger, the christmas tree could be installed using a cable and the open water riser could be eliminated entirely, which would result in significant cost savings for the operator. Therefore, a need exists for a means for retrieving the wireline plug from the tubing hanger which does not require the use of an open water riser.